Digital data transmissions over wired and wireless links sometimes may be corrupted, for instance, by noise in the link or channel, by interference from other transmissions, or by other environmental factors. Even with clear communication channels, which lend themselves to high data rates, it may not be possible to appropriately decode the data stream with the requisite error rates. In order to solve this problem, many current communication systems employ an automatic repeat request (ARQ) scheme for retransmission. In such systems an opportunity exists for requesting that data be retransmitted upon detection of an error. In more complex systems a hybrid ARQ scheme is employed.
In systems employing a hybrid ARQ (H-ARQ) scheme, a receiver combines previously received erroneous transmissions of a packet of information with a newly received transmission in an effort to successfully ascertain the true contents of the packet. In other words, coded bits received on a first erroneous transmission are stored and combined with the coded bits received on later transmissions thereby increasing the likelihood of a correct decoding on later transmissions. Similarly the coded bits received on the second or later transmissions are stored for combining with subsequent received bits.
As one of ordinary skill in the art will recognize, the form of H-ARQ utilized by any communication system is directly dependent upon the type of coding mode utilized. For example, a system employing multiple types of forward error correction (FEC) modes, like Convolutional Codes (CC), Block Turbo Codes (BTC), Convolutional Turbo Codes (CTC) and Low Density Party Check Codes (LDPC), must identify which FEC mode is being utilized in conjunction with the H-ARQ. Moreover, many parameters like the information block size, resource allocation size and incremental redundancy version will be dependent on the FEC mode. With next-generation communication systems employing multiple coding modes, it is impossible to utilize a single H-ARQ signaling scheme and cover all available FEC modes. Therefore a need exists for a method and apparatus to a multi-mode hybrid ARQ within a communication system employing several coding modes.